WO1993003355A1 - Device for sensing volatile materials - Google Patents
Device for sensing volatile materials Download PDFInfo
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- WO1993003355A1 WO1993003355A1 PCT/GB1992/001401 GB9201401W WO9303355A1 WO 1993003355 A1 WO1993003355 A1 WO 1993003355A1 GB 9201401 W GB9201401 W GB 9201401W WO 9303355 A1 WO9303355 A1 WO 9303355A1
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- counter
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- monomer
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
- G01N27/126—Composition of the body, e.g. the composition of its sensitive layer comprising organic polymers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
Definitions
- the present invention relates to a device for detecting volatile materials and in particular the taste and aroma of foodstuffs and beverages such as beer, c Background Art
- the present invention is concerned with a device having an array of sensors' each of which has a different response to a volatile material or a mixture of volatile materials, such as an odour, so that a "fingerprint" of the odour can be built up from the response given by the sensors in the array.
- Each sensor in the array is composed of a
- Each sensor can differ from other sensors in the array as a result of the different polymer used, e.g. one polymer could be polypyrrole and another couldbe poly(N-methylpyrrole) .
- two (or more) sensors can utilise the same basic polymer (e.g. both could be polypyrrole) but their responses could differ because the polymer is grown in the presence of a different counter-ion. This difference arises because the polymer must be oxidised in order to be conducting and so, to balance the charge in the polymer, counter-ions are incorporated into the polymer, e.g. in a proportion of approximately one counter-ion to four monomer units. The nature of the counter-ion alters the resisting characteristics of the polymer when exposed to volatile material(s) . Another factor affecting the resistivity characteristics of the polymer when exposed to volatile material(s) is the solvent used when growing the polymer.
- the polymer used in the sensors can, for example, be chosen from: polypyrrole, poly N-methylpyrrole, poly 3-methylthiophene, polyaniline, poly-5-carboxyindole, poly-3-methyldiphenylamine, polybi hiophene, polythiophene, poly-3-thiopheneacetic acid and polyfuran.
- Typical counter-ions that can be used in growing the polymer of the sensors may be one or more of: tetrafluoroborate, alkyl sulphonates, tetramethylammonium chloride, chlorates and perchlorates.
- Solvents used in polymer growth can be or include water, ethanol or acetonitrile.
- the present invention provides improvements in the above system. Disclosure of the Invention
- a device for sensing volatile materials comprising:
- a plurality of sensors each comprising a pair of spaced-apart electrical contacts and a semi-conductor polymer extending between the contacts, wherein the polymer is such that its electrical resistance can change when exposed to a volatile material
- (b) means for measuring the electrical resistance (or a parameter varying therewith) of the semi-conductor polymer of each sensor, wherein the typical distance between the contacts across which the polymer extends is up to 25 ⁇ m, advantageously in the range of 7 to 13 ⁇ m, more preferably 9 to 11 ⁇ m and most preferably about 10 ⁇ m.
- a further advantage of the present invention is that the response time of the sensors is shortened as compared to the prior art.
- the polymers of the sensor are preferably grown electrochemically by placing the contacts of each sensor in a solution containing a monomer precursor of the polymer and a counter-ion and establishing a potential difference between the contacts and a reference electrode and ⁇ wherein a counter electrode is also provided and the potential between the contacts and the reference electrode is controlled by a potentiostatic circuit that maintains the potential of the two contacts at a substantially fixed or cyclically scanned potential with respect to the reference electrode and wherein the potentiostatic circuit causes a current to flow between the contacts and the counter electrode.
- the reference electrode may be a standard calomel electrode or an Ag/AgCl electrode.
- a potential of approximately 1 volt should be applied between the two contacts (typical value of IV) and the counter electrode in order to grow the polymer.
- the advantage of this aspect of the present invention is that the growth of the polymer can be achieved in a more reproducible manner than is the case when a potential is simply applied between the contacts and a counter electrode and so the sensor thus formed will give more reproducible results.
- the polymer is preferably (but not necessarily) grown on a substrate, which is most preferably an alumina substrate or a fused quartz substrate; other suitable substrate materials may be envisaged by persons skilled in the art.
- a small potential difference can be maintained between the two contacts of the sensor or a small amplitude a.c. signal can be applied across the two contacts of the sensor to monitor the growth of the semi- conductor polymer using a bipotentiostatic circuit; polymer growth may be terminated when the resistance of the semi-conductor polymer during its growth reaches a threshold value.
- a potential difference may be maintained between the contacts and a reference electrode which is lower than that at which substantial polymer growth occurs.
- maintaining the polymer at a potential lower than the growth potential allows equilibration of the counter-ion within the polymer. It is also possible, according to this aspect of the present invention, to change the counter-ion in the polymer by removing the polymer from the solution in which it was grown and dipping it into a further solution containing a different counter-ion and maintaining the polymer at the said potential lower than the polymer growth potential until the substitute counter-ion has replaced the original counter-ions in the polymer.
- the contacts and the polymer are preferably supported on an alumina substrate which provides excellent adhesion between the polymer and the substrate.
- the sensors may each be made by depositing a metal (preferably gold) onto a substrate (preferably onto an alumina substrate) to form the said contacts, depositing a photoresist mask over the electrodes, which mask exposes a locus corresponding to the desired position of the polymer (the locus of the polymer being a limited area between the contacts together with parts overlying the two contacts that enable electrical contact to be established between the contacts and the polymer), dipping the substrate into a solution of a monomer precursor of the polymer and applying a potential difference between the contacts and a reference electrode to cause the monomer precursor to polymerise between the contacts in the said locus.
- a metal preferably gold
- the photoresist which will be of a low bake type and electrochemically inert, preferably covers the whole of the contacts except for the locus of the polymer and a further area allowing the contacts to be connected to external detecting and controlling circuit.
- the photoresist can remain in place to protect the contacts in use and thus improve the ruggedness of the sensor, which prevents damage to the ⁇ contacts and in particular prevents the contacts from exfoliating from the substrate.
- Figure 1 shows a mask for use in making a sensor in accordance 10 with the present invention
- FIG. 2 shows a partly made sensor in accordance with the present invention
- Figure 3 shows a further mask for use in making a sensor in accordance with the present invention
- FIG. 4 shows a partly made sensor in accordance with the present invention
- Figure 5 shows a third mask for use in making a sensor in accordance with the present invention.
- Figure 6 is a schematic drawing of three sensors for use in the device of the present invention. Best Modes for Carrying out the Invention
- a 0.5 inch (1.25 cm) square tile made of alumina is used as a substrate for a sensor and the sensor was built up on it as follows: 0
- a layer of gold 500 Angstrom thick was vapour-deposited over one side of the square tile.
- a photoresist (Shipley positive TF-16) was applied to the substrate by spinning for 15 seconds. 5 (4) The substrate covered by the resist was soft-baked in an oven for 20 minutes at 90°C.
- a mask 12 (shown in Figure 1 where the shaded area are translucent) was placed against the resist and the resist was exposed to ultra-violet light through the mask for 4 minutes.
- the gold was etched using a gold-etchant; the etching time was 1 minute.
- a brass mask (shown in Figure 3 where the holes cut in the mask are shaded) was placed against the substrate and chromium was vapour-deposited on top of the gold contacts to form contact pads for forming electrical connections to a monitoring circuit.
- the substrate, contacts and contact pads 16 are shown in Figure 4. Alternatively, the contact pads may be deposited after the polymer growth.
- the photoresist was exposed to ultra-violet light through a mask 18 (shown in Figure 5, the shaded areas being opaque) for 12 minutes.
- the photoresist was developed using equal parts of Shipley 351 developer diluted with water; the developing time was 1 minute.
- the substrate was then washed in distilled water and hard- baked at 180°C for 1 hour; this temperature caused the photoresist to become insoluble in the various solutions used in the electrochemical growth of the polymer.
- the masked substrate was cleaned by cycling in 1 molar sulphuric acid between -0.3 and 1.8 volts at 100 millivolts/second for 3 cycles. After cleaning, the substrate was stored in pure water until required.
- the polymer is maintained in the monomer solution at a potential less than the growth potential for a sufficient time to ensure the concentration of counter-ions in the polymer has equilibrated.
- the device is washed in the solvent used to make the growth solution. This removes any surface debris and prevents any drying marks due to electrolyte deposition.
- Figure 6 shows the tile bearing three sensors. For ease of illustration, -the top photoresist, which covers the whole of the tile 10 except for the contact pads 16 and the areas 20 in which the polymer
- the resistivity of the polymer 20 between each pair of contacts 12 is measured by passing a current through the polymer by means of the contacts.
- the resistivity of each sensor is analysed using known pattern-recognition techniques to give an indication of the volatile material(s) present in a sample to which the sensors are exposed. 5
- the following solutions of monomers have been used successfully to grow polymers between the contacts:
- the polypyrrole produced was smooth, strong and black.
- the polymer had to be held at a potential below the growth potential (0.9V) to allow equilibration of the counter -ions in the polymer otherwise the polymer was non- conductive .
- the films are dense, black and smooth with good adhesion.
- DC resistance is typically 50 ⁇ .
- the films are dense, black and smooth with good adhesion.
- DC resistance is typically 50 ⁇ .
- Sensors having different semi-conductive polymers and/or having polymers growth in the presence of different counter-ions or in the presence of different solvents can be combined into an array. hen the array of sensors is exposed to a volatile vapour, the change in the conductivity of the polymer of each sensor is measured and the response given by the sensors in the array will depend on the nature of the volatile materials, different volatile materials generally giving different response patterns. These different response patterns can be recognised using known pattern recognition techniques to give a response giving an indication of the nature of the volatile materials in the vapour.
- This array has been able to distinguish between different brands of lager beer and between two samples of the same beer that had been stored differently.
Abstract
A device is described for sensing volatile materials, the device comprising: a) a plurality of sensors each comprising a pair of spaced-apart electrical contacts (12) and a semi-conductor polymer extending between the contacts, wherein the polymer is such that its electrical resistance can change when exposed to a volatile material; and b) means for measuring the electrical resistance (or a parameter varying therewith) of the semi-conductor polymer of each sensor. The distance between the contacts across which the polymer extends is up to 25 νm, or in the range of 7 to 13 νm, more preferably 9 to 11 νm and most preferably about 10 νm.
Description
Device for Sensing Volatile Materials Technical Field
The present invention relates to a device for detecting volatile materials and in particular the taste and aroma of foodstuffs and beverages such as beer, c Background Art
Currently, there is no device commercially available for assessing the quality of a product based on its taste and aroma and this task is usually performed by tasting panels. However, tasting panels are expensive to convene, are not always able to detect the subtle changes in taste or aroma and it is not economic to monitor the quality of, for example, all batches of beer produced in a large 10 brewery using a tasting panel. The same is true of other beverages and foodstuffs not only for human consumption but also for animal consumption.
It is known from International Application No.86/01599 (Persaud et al) and an article by Pelosi and Persaud ('Gas Sensors: Towards an Artificial Nose' NATO ASI Series, Vol F43, Sensors and Sensory Systems for Advanced Robots. Ed-P. Dario, Springer-Verlag Berlin Heidelberg
15 1988) to detect odours and gases by means of a device that is said to mimic the olfactory system.
The present invention is concerned with a device having an array of sensors' each of which has a different response to a volatile material or a mixture of volatile materials, such as an odour, so that a "fingerprint" of the odour can be built up from the response given by the sensors in the array. Each sensor in the array is composed of a
20 pair of contacts that are bridged by an organic semi-conducting polymer such as polypyrrole that may be grown electrochemically in the presence of a counter-ion between the two contacts. In each sensor of the array the resistance across the semi-conductor polymer is measured and because the polymers in the sensors in the array are different, their resistance changes in a different way on exposure to the volatile 25 material(s). In this way, the fingerprint of the odour can be built up. For example, the polymers of certain sensors will interact with (possibly by absorption) low molecular weight materials more readily
4 than the polymers of other sensors and accordingly the polymers that
'_
interact with the low molecular weight components of an odour will give a different response to those that do not interact with such low molecular weight components.
Each sensor can differ from other sensors in the array as a result of the different polymer used, e.g. one polymer could be polypyrrole and another couldbe poly(N-methylpyrrole) . Alternatively, two (or more) sensors can utilise the same basic polymer (e.g. both could be polypyrrole) but their responses could differ because the polymer is grown in the presence of a different counter-ion. This difference arises because the polymer must be oxidised in order to be conducting and so, to balance the charge in the polymer, counter-ions are incorporated into the polymer, e.g. in a proportion of approximately one counter-ion to four monomer units. The nature of the counter-ion alters the resisting characteristics of the polymer when exposed to volatile material(s) . Another factor affecting the resistivity characteristics of the polymer when exposed to volatile material(s) is the solvent used when growing the polymer.
The polymer used in the sensors can, for example, be chosen from: polypyrrole, poly N-methylpyrrole, poly 3-methylthiophene, polyaniline, poly-5-carboxyindole, poly-3-methyldiphenylamine, polybi hiophene, polythiophene, poly-3-thiopheneacetic acid and polyfuran.
Typical counter-ions that can be used in growing the polymer of the sensors may be one or more of: tetrafluoroborate, alkyl sulphonates, tetramethylammonium chloride, chlorates and perchlorates. Solvents used in polymer growth can be or include water, ethanol or acetonitrile.
Unfortunately, the polymers in the sensors tend to degrade rapidly, resulting in sensors having only a relatively short operational lifespan.
The present invention provides improvements in the above system. Disclosure of the Invention
In accordance with the present invention, there is provided a device for sensing volatile materials, the device comprising:
(a) a plurality of sensors each comprising a pair of spaced-apart electrical contacts and a semi-conductor polymer extending between the contacts, wherein the polymer is such that its electrical resistance
can change when exposed to a volatile material, and
• (b) means for measuring the electrical resistance (or a parameter varying therewith) of the semi-conductor polymer of each sensor, wherein the typical distance between the contacts across which the polymer extends is up to 25 μm, advantageously in the range of 7 to 13 μm, more preferably 9 to 11 μm and most preferably about 10 μm.
We have found that by providing a spacing between the contacts of 10 μm ± 3 μm (as opposed to a spacing of about 100 μm in prior art sensors) the polymer does not degrade as rapidly and so the life-span. of the sensors in the device of the present invention is extended. A further advantage of the present invention is that the response time of the sensors is shortened as compared to the prior art. The polymers of the sensor are preferably grown electrochemically by placing the contacts of each sensor in a solution containing a monomer precursor of the polymer and a counter-ion and establishing a potential difference between the contacts and a reference electrode and ■ wherein a counter electrode is also provided and the potential between the contacts and the reference electrode is controlled by a potentiostatic circuit that maintains the potential of the two contacts at a substantially fixed or cyclically scanned potential with respect to the reference electrode and wherein the potentiostatic circuit causes a current to flow between the contacts and the counter electrode.
The reference electrode may be a standard calomel electrode or an Ag/AgCl electrode. A potential of approximately 1 volt should be applied between the two contacts (typical value of IV) and the counter electrode in order to grow the polymer. The advantage of this aspect of the present invention is that the growth of the polymer can be achieved in a more reproducible manner than is the case when a potential is simply applied between the contacts and a counter electrode and so the sensor thus formed will give more reproducible results. The polymer is preferably (but not necessarily) grown on a substrate, which is most preferably an alumina substrate or a fused quartz substrate; other suitable substrate materials may be envisaged by persons skilled in the art.
It is possible to regulate the amount of polymer grown by
terminating the polymer growth after a predetermined period of time or when a predetermined amount of current has passed. Alternatively, a small potential difference can be maintained between the two contacts of the sensor or a small amplitude a.c. signal can be applied across the two contacts of the sensor to monitor the growth of the semi- conductor polymer using a bipotentiostatic circuit; polymer growth may be terminated when the resistance of the semi-conductor polymer during its growth reaches a threshold value.
After the polymer has been grown, a potential difference may be maintained between the contacts and a reference electrode which is lower than that at which substantial polymer growth occurs. We have found that maintaining the polymer at a potential lower than the growth potential allows equilibration of the counter-ion within the polymer. It is also possible, according to this aspect of the present invention, to change the counter-ion in the polymer by removing the polymer from the solution in which it was grown and dipping it into a further solution containing a different counter-ion and maintaining the polymer at the said potential lower than the polymer growth potential until the substitute counter-ion has replaced the original counter-ions in the polymer.
The contacts and the polymer are preferably supported on an alumina substrate which provides excellent adhesion between the polymer and the substrate.
In accordance with a preferred aspect, the sensors may each be made by depositing a metal (preferably gold) onto a substrate (preferably onto an alumina substrate) to form the said contacts, depositing a photoresist mask over the electrodes, which mask exposes a locus corresponding to the desired position of the polymer (the locus of the polymer being a limited area between the contacts together with parts overlying the two contacts that enable electrical contact to be established between the contacts and the polymer), dipping the substrate into a solution of a monomer precursor of the polymer and applying a potential difference between the contacts and a reference electrode to cause the monomer precursor to polymerise between the contacts in the said locus.
The photoresist, which will be of a low bake type and
electrochemically inert, preferably covers the whole of the contacts except for the locus of the polymer and a further area allowing the contacts to be connected to external detecting and controlling circuit. The photoresist can remain in place to protect the contacts in use and thus improve the ruggedness of the sensor, which prevents damage to the ς contacts and in particular prevents the contacts from exfoliating from the substrate.
Brief Description of Drawings
The present invention will now be described in further detail with reference to the accompanying drawings, in which:
Figure 1 shows a mask for use in making a sensor in accordance 10 with the present invention;
Figure 2 shows a partly made sensor in accordance with the present invention;
Figure 3 shows a further mask for use in making a sensor in accordance with the present invention;
Figure 4 shows a partly made sensor in accordance with the present invention and 5
Figure 5 shows a third mask for use in making a sensor in accordance with the present invention.
Figure 6 is a schematic drawing of three sensors for use in the device of the present invention. Best Modes for Carrying out the Invention
A 0.5 inch (1.25 cm) square tile made of alumina is used as a substrate for a sensor and the sensor was built up on it as follows: 0
(1) A layer of gold 500 Angstrom thick was vapour-deposited over one side of the square tile.
(2) Dust particles are removed from the gold-coated substrate by washing it with xylene.
(3) A photoresist (Shipley positive TF-16) was applied to the substrate by spinning for 15 seconds. 5 (4) The substrate covered by the resist was soft-baked in an oven for 20 minutes at 90°C.
(5) A mask 12 (shown in Figure 1 where the shaded area are translucent) was placed against the resist and the resist was exposed
to ultra-violet light through the mask for 4 minutes.
(6) The unexposed area of the photoresist was removed using Shipley MF-319 developer for 1 minute.
(7) The gold-coated substrate was washed in distilled water and hard-baked in an oven for 1 hour at 115°C to render the resist insoluble to an etchant used in step (8) below.
(8) At the area where the resist was removed, the gold was etched using a gold-etchant; the etching time was 1 minute.
(9) The remaining photoresist was removed using acetone and the substrate was washed in distilled water. Thus, referring to Figure 2, the substrate 10 bears a gold image of mask 12 and this image forms three pairs of contacts 14 each pair of contacts being part of a different sensor. The contacts of each pair are separated by a gap 15 to 10 μm in width.
(10) A brass mask (shown in Figure 3 where the holes cut in the mask are shaded) was placed against the substrate and chromium was vapour-deposited on top of the gold contacts to form contact pads for forming electrical connections to a monitoring circuit. The substrate, contacts and contact pads 16 are shown in Figure 4. Alternatively, the contact pads may be deposited after the polymer growth.
(11) Xylene was spun over the surface of the substrate to remove any dust particles.
(12) A Shipley 1813 photoresist was spun over the surface of the substrate for 15 seconds.
(13) The substrate bearing the contacts and the contact pads was soft-baked in an oven for 5 minutes at 90°C.
(14) The photoresist was exposed to ultra-violet light through a mask 18 (shown in Figure 5, the shaded areas being opaque) for 12 minutes.
(15) The photoresist was developed using equal parts of Shipley 351 developer diluted with water; the developing time was 1 minute.
(16) The substrate was then washed in distilled water and hard- baked at 180°C for 1 hour; this temperature caused the photoresist to become insoluble in the various solutions used in the electrochemical growth of the polymer.
(17) The masked substrate was cleaned by cycling in 1 molar
sulphuric acid between -0.3 and 1.8 volts at 100 millivolts/second for 3 cycles. After cleaning, the substrate was stored in pure water until required.
(18) The masked substrate was placed in a monomer solution (details of the composition of which are given below) and both contacts c of the device are connected to a potentiostatic circuit that maintains the potential of the contacts substantially with respect to a calomel reference electrode; a counter electrode is also provided.
(19) The potential between the contacts and a reference electrode is stepped or cycled to a predetermined working voltage to begin growth. After the desired time, the potential is stepped back to 0 V. If after viewing the device under the microscope or by measuring the
10 resistance of the polymer it becomes apparent that the gap between the contacts has not been crossed, then the electrode can be returned to the working solution and further growth performed.
(20) The polymer is maintained in the monomer solution at a potential less than the growth potential for a sufficient time to ensure the concentration of counter-ions in the polymer has equilibrated.
15
(21) The device is washed in the solvent used to make the growth solution. This removes any surface debris and prevents any drying marks due to electrolyte deposition.
(22).The conductivity of the polymer was then tested. Figure 6 shows the tile bearing three sensors. For ease of illustration, -the top photoresist, which covers the whole of the tile 10 except for the contact pads 16 and the areas 20 in which the polymer
20 is deposited, has been omitted. In use, the resistivity of the polymer 20 between each pair of contacts 12 is measured by passing a current through the polymer by means of the contacts. The resistivity of each sensor is analysed using known pattern-recognition techniques to give an indication of the volatile material(s) present in a sample to which the sensors are exposed. 5 The following solutions of monomers have been used successfully to grow polymers between the contacts:
1) Monomer concentration : 0.1 M pyrrole
Counter- ion concentration 0.1 M tetraethyl- ammonium tetrafluoroborate
Solvent Water Growth method Potential step 0 to 0.8 V Growth time 3 minutes
The polypyrrole produced was smooth, strong and black.
2) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M lithium triflate
Solvent Water
Growth method Potential step 0-0.9 V
Growth time 4 minutes
The polymer had to be held at a potential below the growth potential (0.9V) to allow equilibration of the counter -ions in the polymer otherwise the polymer was non- conductive .
3) Monomer concentration 0.1 M N-methylpyrrole Counter-ion concentration 0.1 M sodium salt of dodecylbenzene sulphonic acid
Solvent Water Growth method Potential step
0 - (07.-0.9) V
Growth time at least 16 minutes
4) Monomer concentration 0.1 M 3-methylthiophene Counter-ion concentration 0.1 M tetraethylammoniu tetrafluoroborate
Solvent Acetonitrile Growth method Potential step 0 - 1.65 V
Growth time .3 minutes
5) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M tetraethylammmonium toluene-sulphonate
Solvent Water
Growth method Potential step 0 0.8 V Growth time 3 minutes
6) Monomer concentration 0.1 M 3-me hyldiphenyl- amine
Counter-ion concentration 0.1 M LiC10« Solvent Acetonitrile Growth method Potential step 0 - 1.0 V Growth time 2 minutes
7) Monomer concentration 0.05 M 2,2' -bithiophene Counter-ion concentration 0.1 M tetraethyl- ammonium tetrafluoro¬ borate
Solvent Acetonitrile Growth method Potential step 0 - 1.65 V Growth time . 3 minutes
8) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M octanesulphonic acid
Solvent Water
Growth method Potential step 0 - 0.8 V
Growth time 2 minutes
The films are dense, black and smooth with good adhesion. DC resistance is typically 50 Ω.
9) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M hexanesulphonic acid
Solvent Water
Growth method Potential step 0 - 0.8 V
Growth time 2 minutes
The films are dense, black and smooth with good adhesion. DC resistance is typically 50 Ω.
10) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.001 M anthraquinone-2-
sulphonic acid
Solvent Water Growth method Potential step 0 - 1.15 V Growth time 2 minutes
11) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M butanesulphonic acid Solvent Water Growth method Potential step 0 - 0.85 V Growth time 2 minutes
12) Monomer concentration 0.1 M pyrrole Counter-ion concentration 0.1 M pentanesulphonic acid Solvent Water
Growth method Potential step 0 - 0.85 V Growth time 2 minutes
13) Monomer concentration 0.1 M pyrrole Counter-ion concentration 0.1 M heptanesulphonic acid Solvent Water
Growth method Potential step 0 - 0.85 V Growth time 2 minutes
14) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M decanesulphonic acid Solvent Water Growth method Potential step 0 - 0.85 V Growth time 2 minutes
15) Monomer concentration 0.44 M aniline
Counter-ion concentration 0.5 M NaHS04,Ph 1 Solvent Water Growth method Potential step 0 - 0.9 V Growth time 2 minutes
16) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M p- toluene sulphonic
acid
Solvent Ethanol Growth method Potential step 0 - 1.2 V Growth time 2 minutes
17) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M tetraethylammonium tetrafluoroborate
Solvent Acetonitrile Growth method Potential step 0 - 1.1 V Growth time 2 minutes
Sensors having different semi-conductive polymers and/or having polymers growth in the presence of different counter-ions or in the presence of different solvents can be combined into an array. hen the array of sensors is exposed to a volatile vapour, the change in the conductivity of the polymer of each sensor is measured and the response given by the sensors in the array will depend on the nature of the volatile materials, different volatile materials generally giving different response patterns. These different response patterns can be recognised using known pattern recognition techniques to give a response giving an indication of the nature of the volatile materials in the vapour.
An array of eleven sensors that we have used is as follows:
Sensor No. Type of polymer/counter-ion/solvent 0 Polypyrrole/butanesulphonate/water 1 Polypyrrole/butanesulphonate/water 2 Polypyrrole/toluenesulphonate/ethanol 3 Polypyrrole/toluenesulphonate/ethanol 4 Polypyrrole/tetraethyleneammonium toluene- sulphonate/water
Polypyrrole/tetraethyleneammonium toluene- sulphonate/water
Poly-3-methylthiophene/tetraethyleneammonium- tetrafluoroborate/acetonitrile
7 Polypyrrole/propanesulphonate/water 8 Polypyrrole/propanesulphonate/water
9 Polyaniline/bisulphate/water
10 Polyaniline/bisulphate/water
This array has been able to distinguish between different brands of lager beer and between two samples of the same beer that had been stored differently.
Claims
CLAIMS 1. A device for sensing volatile materials, the device comprising:
(a) a plurality of sensors each comprising a pair of spaced-apart electrical contacts and a semi-conductor polymer extending between the contacts, wherein the polymer is such that its electrical resistance s can change when exposed to a volatile material, and
(b) means for measuring the electrical resistance (or a parameter varying therewith or functionally related thereto) of the semi¬ conductor polymer of each sensor, wherein (preferably) in that the distance between the contacts in each sensor across which the polymer extends is up to 25 μm, more preferably 7 to 13 μm, 9 to 11 μm and most preferably about 10 μm.
10 2 A device as claimed in claim 1, wherein the contacts and the polymer of each sensor are supported on a substrate, e.g. an alumina or fused quartz substrate.
3 A device as claimed in claim 1, which includes a photoresist which covers each sensor except for the locus of the polymer.
4 A method of making a device according to claim 1, which comprises growing the polymer of each sensor electroche ically by placing the
15 contacts of each sensor in a solution containing a monomer precursor of the polymer and a counter-ion and establishing a potential difference between the contacts and a counter electrode, thereby causing the monomer to. polymerise between contacts.
5 A method as claimed in claim 4, wherein a reference electrode is also provided and wherein a substantially constant potential or a cyclically scanned potential is maintained between the contacts and the
20 reference electrode by means of an electrical circuit during polymerisation of the monomer, which circuit causes a current to flow between the contacts and the counter electrode.
6 A method as claimed in claim 4, wherein a constant, alternating or periodic potential difference is imposed between the contacts and wherein the polymer growth is terminated when the resistance of the
25 polymer during its growth reaches a threshold value.
7 A method as claimed in claim 4, wherein, after the polymer has been grown, a potential difference is maintained between the contacts and the counter electrode, which potential is lower than that at which
substantial polymer growth occurs, thereby equilibrating the concentration of the counter-ion within the polymer.
8 A method as claimed in claim 4, which further comprises, prior to growing the polymer, depositing the contacts of each sensor onto a substrate, depositing a photoresist mask over the contacts, which mask leaves exposed a limited area between the contacts corresponding to the desired position of the polymer and wherein the polymer is grown in the said limited area.
9 A method as claimed in claim 4, wherein the polymer of at least one of the sensors is grown form a monomer electrolyte selected form the following: a) Monomer concentration : 0.1 M pyrrole
Counter-ion concentration : 0.1 M tetraethyl- ammonium tetrafluoroborate Solvent : Water
b) Monomer concentration 0.1 M pyrrole Counter-ion concentration 0.1 M lithium triflate Solvent Water
c) Monomer concentration 0.1 M N-methylpyrrole Counter-ion concentration 0.1 M sodium salt of dodecylbenzene sulphonic acid
Solvent Water
d) Monomer concentration 0.1 M 3-methylthiophene
Counter-ion concentration 0.1 M tetraethylammonium tetrafluoroborate
Solvent Acetonitrile
e) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M tetraethylammmonium toluene-sulphonate
Solvent Water
f) Monomer concentration 0.1 M 3-methyldiphenyl-
aπαne
Counter- ion concentration 0.1 M LiCIO* Solvent Acetonitrile
g) Monomer concentration 0.05 M 2 , 2 ' -bithiophene
Counter-ion concentration 0.1 M tetraethylammonium tetrafluoroborate
Solvent Acetonitrile
h) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M octanesulphonic acid Solvent Water
i) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M hexanesulphonic acid Solvent Water
j ) Monomer concentration 0.1 M pyrrole
Counter- ion concentration 0.001 M anthraquinone-2- sulphonic acid
Solvent Water
k) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M butanesulphonic acid Solvent Water
1) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M pentanesulphonic acid Solvent Water
m) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M heptanesulphonic acid Solvent Water
n) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M decanesulphonic acid
Solvent Water
o) • Monomer concentration 0.44 M aniline
Counter-ion concentration 0.5 M NaHS04,Ph 1 Solvent Water
p) Monomer concentration 0.1 M pyrrole
Counter-ion concentration 0.1 M p-toluene sulphonic acid
Solvent Ethanol
q) Monomer concentration 0.1 M pyrrole Counter-ion concentration 0.1 M tetraethylammonium tetrafluoroborate
Solvent Acetonitrile
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP92916413A EP0596973B1 (en) | 1991-07-29 | 1992-07-29 | Device for sensing volatile materials |
| DE69207197T DE69207197T2 (en) | 1991-07-29 | 1992-07-29 | GAS SENSOR |
| JP5503385A JPH06509869A (en) | 1991-07-29 | 1992-07-29 | Device for detecting volatile substances |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB919116360A GB9116360D0 (en) | 1991-07-29 | 1991-07-29 | Device for sensing volatile materials |
| GB9116360.0 | 1991-07-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1993003355A1 true WO1993003355A1 (en) | 1993-02-18 |
Family
ID=10699174
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/GB1992/001401 WO1993003355A1 (en) | 1991-07-29 | 1992-07-29 | Device for sensing volatile materials |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0596973B1 (en) |
| JP (1) | JPH06509869A (en) |
| AT (1) | ATE132262T1 (en) |
| CA (1) | CA2113544A1 (en) |
| DE (1) | DE69207197T2 (en) |
| GB (1) | GB9116360D0 (en) |
| WO (1) | WO1993003355A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995023335A1 (en) * | 1994-02-25 | 1995-08-31 | Neotronics Limited | Monitor and method for detecting volatile materials |
| WO1995023964A1 (en) * | 1994-03-03 | 1995-09-08 | Neotronics Limited | Gas sensor assembly and method of fabrication thereof |
| WO1995025268A1 (en) * | 1994-03-16 | 1995-09-21 | Neotronics Limited | Sample testing vessel and method |
| WO1995032420A1 (en) * | 1994-05-20 | 1995-11-30 | Quest International B.V. | Method for substrate classification |
| WO1995032422A1 (en) * | 1994-05-23 | 1995-11-30 | Aromascan Plc | Sensor |
| WO1995033991A1 (en) * | 1994-06-09 | 1995-12-14 | Aromascan Plc | Condition indicator |
| WO1996007901A1 (en) * | 1994-09-06 | 1996-03-14 | Mastiff Electronic Systems Ltd | Odour sensor |
| WO1996042011A1 (en) * | 1995-06-09 | 1996-12-27 | Aromascan Plc | Integrated sensor |
| EP0794428A1 (en) * | 1996-03-04 | 1997-09-10 | Neotronics Limited | Sensor for volatile materials and gases |
| ES2121699A1 (en) * | 1996-12-10 | 1998-12-01 | Consejo Superior Investigacion | Portable system for determining volatile organic compounds in soils. |
| WO1999026061A1 (en) * | 1997-11-13 | 1999-05-27 | Osmetech Plc | Gas sensor |
| EP0945723A1 (en) * | 1998-03-26 | 1999-09-29 | Danilo De Rossi | Process for preparing electro-conductive polymer films by doping neutral polymers |
| WO1999049305A1 (en) * | 1998-03-20 | 1999-09-30 | Osmetech Plc | Sensor manufacture |
| WO2000037933A1 (en) * | 1998-12-18 | 2000-06-29 | Raytheon Company | Stochastic array processing of sensor measurements to detect and quantify analytes |
| US6170318B1 (en) * | 1995-03-27 | 2001-01-09 | California Institute Of Technology | Methods of use for sensor based fluid detection devices |
| EP1411552A2 (en) | 2002-09-25 | 2004-04-21 | STMicroelectronics, Inc. | Organic semiconductor sensor device |
| ES2268973A1 (en) * | 2005-05-23 | 2007-03-16 | Consejo Superior Investig. Cientificas | Automatic system for the continuous analysis of the evolution of wine |
| CN100350239C (en) * | 2005-03-31 | 2007-11-21 | 浙江大学 | Polypyrrol gas sensitive sensor |
| WO2008059095A1 (en) | 2006-11-14 | 2008-05-22 | Consejo Superior De Investigaciones Científicas | Organic sensor device and its applications |
| US7837844B2 (en) * | 2005-04-26 | 2010-11-23 | Seacoast Science, Inc. | Interdigitated chemical sensors, and methods of making and using the same |
| WO2012087247A3 (en) * | 2010-12-22 | 2012-10-18 | Institut "Jožef Stefan" | An array smell sensor based on the measurement of the junction impedance of nanowires with different metals |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5607573A (en) * | 1993-03-10 | 1997-03-04 | Hughes Aircraft Company | Method for detecting fugitive emissions |
| US5951846A (en) * | 1995-03-27 | 1999-09-14 | California Institute Of Technology | Sensor arrays for detecting analytes in fluids |
| US5756879A (en) * | 1996-07-25 | 1998-05-26 | Hughes Electronics | Volatile organic compound sensors |
| WO1999000663A1 (en) | 1997-06-30 | 1999-01-07 | California Institute Of Technology | Compositionally different polymer-based sensor elements and methods for preparing same |
| US6730212B1 (en) | 2000-10-03 | 2004-05-04 | Hrl Laboratories, Llc | Sensor for chemical and biological materials |
| US7008524B2 (en) | 2000-10-03 | 2006-03-07 | Hrl Laboratories, Llc | Sensors with variable response behavior |
| US7200348B2 (en) | 2004-06-29 | 2007-04-03 | Samsung Electronics Co., Ltd | Volatile organic compound detector |
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| US4415876A (en) * | 1980-01-25 | 1983-11-15 | Nippon Soken, Inc. | Gas sensor |
| WO1986001599A1 (en) * | 1984-08-21 | 1986-03-13 | Cogent Limited | Gas sensors, and methods of making and using them |
| GB2203249A (en) * | 1987-02-03 | 1988-10-12 | Univ Warwick | Identifying or measuring components of a mixture |
| US5034192A (en) * | 1984-11-23 | 1991-07-23 | Massachusetts Institute Of Technology | Molecule-based microelectronic devices |
-
1991
- 1991-07-29 GB GB919116360A patent/GB9116360D0/en active Pending
-
1992
- 1992-07-29 DE DE69207197T patent/DE69207197T2/en not_active Revoked
- 1992-07-29 CA CA002113544A patent/CA2113544A1/en not_active Abandoned
- 1992-07-29 JP JP5503385A patent/JPH06509869A/en active Pending
- 1992-07-29 EP EP92916413A patent/EP0596973B1/en not_active Revoked
- 1992-07-29 AT AT92916413T patent/ATE132262T1/en not_active IP Right Cessation
- 1992-07-29 WO PCT/GB1992/001401 patent/WO1993003355A1/en not_active Application Discontinuation
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4415876A (en) * | 1980-01-25 | 1983-11-15 | Nippon Soken, Inc. | Gas sensor |
| WO1986001599A1 (en) * | 1984-08-21 | 1986-03-13 | Cogent Limited | Gas sensors, and methods of making and using them |
| US5034192A (en) * | 1984-11-23 | 1991-07-23 | Massachusetts Institute Of Technology | Molecule-based microelectronic devices |
| GB2203249A (en) * | 1987-02-03 | 1988-10-12 | Univ Warwick | Identifying or measuring components of a mixture |
Cited By (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995023335A1 (en) * | 1994-02-25 | 1995-08-31 | Neotronics Limited | Monitor and method for detecting volatile materials |
| AU679346B2 (en) * | 1994-03-03 | 1997-06-26 | Neotronics Limited | Gas sensor assembly and method of fabrication thereof |
| WO1995023964A1 (en) * | 1994-03-03 | 1995-09-08 | Neotronics Limited | Gas sensor assembly and method of fabrication thereof |
| WO1995025268A1 (en) * | 1994-03-16 | 1995-09-21 | Neotronics Limited | Sample testing vessel and method |
| WO1995032420A1 (en) * | 1994-05-20 | 1995-11-30 | Quest International B.V. | Method for substrate classification |
| WO1995032422A1 (en) * | 1994-05-23 | 1995-11-30 | Aromascan Plc | Sensor |
| WO1995033991A1 (en) * | 1994-06-09 | 1995-12-14 | Aromascan Plc | Condition indicator |
| US5928609A (en) * | 1994-09-06 | 1999-07-27 | Bloodhound Sensors, Ltd. | Odor sensor |
| WO1996007901A1 (en) * | 1994-09-06 | 1996-03-14 | Mastiff Electronic Systems Ltd | Odour sensor |
| US6170318B1 (en) * | 1995-03-27 | 2001-01-09 | California Institute Of Technology | Methods of use for sensor based fluid detection devices |
| WO1996042011A1 (en) * | 1995-06-09 | 1996-12-27 | Aromascan Plc | Integrated sensor |
| EP0794428A1 (en) * | 1996-03-04 | 1997-09-10 | Neotronics Limited | Sensor for volatile materials and gases |
| ES2121699A1 (en) * | 1996-12-10 | 1998-12-01 | Consejo Superior Investigacion | Portable system for determining volatile organic compounds in soils. |
| WO1999026061A1 (en) * | 1997-11-13 | 1999-05-27 | Osmetech Plc | Gas sensor |
| WO1999049305A1 (en) * | 1998-03-20 | 1999-09-30 | Osmetech Plc | Sensor manufacture |
| US6655010B1 (en) | 1998-03-20 | 2003-12-02 | Osmetech Plc | Method for batch manufacturing sensor units |
| EP0945723A1 (en) * | 1998-03-26 | 1999-09-29 | Danilo De Rossi | Process for preparing electro-conductive polymer films by doping neutral polymers |
| WO2000037933A1 (en) * | 1998-12-18 | 2000-06-29 | Raytheon Company | Stochastic array processing of sensor measurements to detect and quantify analytes |
| US8569809B2 (en) | 2002-09-25 | 2013-10-29 | Stmicroelectronics, Inc. | Organic semiconductor sensor device |
| EP1411552A2 (en) | 2002-09-25 | 2004-04-21 | STMicroelectronics, Inc. | Organic semiconductor sensor device |
| EP1411552A3 (en) * | 2002-09-25 | 2008-07-02 | STMicroelectronics, Inc. | Organic semiconductor sensor device |
| CN100350239C (en) * | 2005-03-31 | 2007-11-21 | 浙江大学 | Polypyrrol gas sensitive sensor |
| US7837844B2 (en) * | 2005-04-26 | 2010-11-23 | Seacoast Science, Inc. | Interdigitated chemical sensors, and methods of making and using the same |
| ES2268973A1 (en) * | 2005-05-23 | 2007-03-16 | Consejo Superior Investig. Cientificas | Automatic system for the continuous analysis of the evolution of wine |
| WO2008059095A1 (en) | 2006-11-14 | 2008-05-22 | Consejo Superior De Investigaciones Científicas | Organic sensor device and its applications |
| US8343436B2 (en) | 2006-11-14 | 2013-01-01 | Consejo Superior De Investigaciones Cientificas | Organic sensor device and its applications |
| WO2012087247A3 (en) * | 2010-12-22 | 2012-10-18 | Institut "Jožef Stefan" | An array smell sensor based on the measurement of the junction impedance of nanowires with different metals |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0596973B1 (en) | 1995-12-27 |
| EP0596973A1 (en) | 1994-05-18 |
| ATE132262T1 (en) | 1996-01-15 |
| CA2113544A1 (en) | 1993-02-18 |
| DE69207197D1 (en) | 1996-02-08 |
| DE69207197T2 (en) | 1996-05-30 |
| JPH06509869A (en) | 1994-11-02 |
| GB9116360D0 (en) | 1991-09-11 |
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